Regulation of Glomerular Filtration Rate. Renal Clearance 1

Question 1

What are Starling Forces?

Answer 1

The mechanisms that control glomerular filtration.

Question 2

What the the factors controlling Starling Forces?

Answer 2

• Hydrostatic P of blood in the glomerular capillaries (Pgc)
• Hydrostatic P of ultrafiltrate in the Bowman’s space (Pbs)
• Oncotic pressure of blood (plasma) in glomerular capillaries (πgc)
  (mean value 32 mmHg)
• oncotic pressure of ultra filtrate in Bowman’s capsule (πbs) - negligible

Question 3

What is the importance of having increased oncotic P of plasma in the peritubular capillaries?

Answer 3

facilitates fluid reabsorption from ISF

Question 4

Where does reabsorption take place in nephron. Which vessels?

Answer 4

peritubular capillaries

Question 5

What is filtration coefficient (Kf)?

Answer 5

the product of water permeability of the glomerular capillary wall & effective filtration surface area of GM

Question 6

What does filtration coefficient depend on?

Answer 6

— Water permeability per unit surface area (hydraulic
conductance)
— Total surface area

Question 7

What does the filtration coefficient depend on?

Answer 7

— Water permeability per unit surface area (hydraulic
conductance)
— Total surface area

Question 8

How does ↑ glomerular surface area due to relaxation of the
mesangeal cells affect GFR?

Answer 8

↑ GFR

Question 9

Reasons for increased Kf.

Answer 9

↑ glomerular surface area due to relaxation of the
mesangeal cells

Question 10

Reasons for decreased Kf?

Answer 10

— ↑ thickness of the basement membrane (i.e., uncontrolled hypertension and diabetes mellitus)
— ↓ number of functional nephrons

Question 11

How does decreased Kf affect GFR?

Answer 11

decreases GFR

Question 12

Effects of afferent arteriole constriction.

Answer 12

↓ RPF (↓ blood inflow into the capillaries) →

↓PGC→↓netfiltrationP→ ↓ GFR

↓hydrostatic P & oncotic P in peritubular capillary → ↑ peritubular reabsorption

Question 13

What are factors that would stimulate constriction of EA?

Answer 13

— Moderate ATII
— Strong sympathetic

Question 14

What are the effects of EA constriction?

Answer 14

— → ↑ PGC → ↑ net filtration P → ↑ GFR (biphasic effect)
— → ↑ FF (↑ GFR & ↓ RPF)
— ↓ peritubular capillary
↓ peritubular capillary hydrostatic P, ↑ oncotic P; ↑ reabsorption
hydrostatic P; ↑ oncotic P

Question 15

Describe effects of increased mean arterial BP on the kidney.

Answer 15

↑ MABP →↑ Capillary hydrostatic P & GFR – pressure diuresis

Question 16

What are reasons for increased oncotic pressure of GC?

Answer 16

— ↑ plasma protein concentration in
the systemic blood
— ↓ renal plasma flow → ↑ oncotic P along glomerular capillaries
— ↑ FF (more than N value of 20%) — Effectsof↑inoncoticPofGC:
— ↓ net filtration P → ↓ GFR — ↓ FF

Question 17

What are reasons for decreased oncotic P of GC?

Answer 17

Reasons: ↓ plasma protein concentration in the systemic blood (i.e., loss of proteins in the urine - nephrotic syndrome)

Effects of ↓ oncotic P of GC: — ↑ net filtration P → ↑ GFR — ↑ FF

Question 18

What are reasons for increased Bowmans capsule hydrostatic pressure?

Answer 18

Reasons:
— ↓ urine outf low (i.e., tubular obstruction, ureteral stone or constriction)

Question 19

What are the effects of increased BC hydrostatic pressure on glomerulus?

Answer 19

— ↓ net ultrafiltration P → ↓ GFR
↓ FF

Question 20

Be able to reproduce this chart.

Answer 20

Reproduce chart.

Question 21

What is the capillary hydrostatic pressure in the peritubular capillaries?

Answer 21

Ppc= 20 mm Hg

Question 22

Why is there low capillary hyrostatic pressure in peritubular capillaries?

Answer 22

due to resistance of efferent arteriole

Question 23

Why is there high plasma oncotic P in peritubular capillaries?

Answer 23

due to filtration of protein-free fluid into Bowman’s capsule

Question 24

What is the plasma oncotic capillary pressure in peritubular capillaries?

Answer 24

35 mmHg

Question 25

Complete this activity.

Answer 25

Complete activity

Question 26

Be able to reproduce this chart.

Answer 26

Reproduce

Question 27

Which one of the following causes an increase in both glomerular filtration rate (GFR) and renal plasma flow?

a. Hyper-proteinemia
b. Constriction of both afferent and efferent arterioles
c. Dilation of the afferent arteriole
d. Dilation of the efferent arteriole
e. Constriction of the efferent arteriole

Answer 27

Constriction of the efferent arteriole